Saṃyutta Nikāya 56
Connected Discourses on the Truths
37. The Sun (1)
“Bhikkhus, this is the forerunner and precursor of the rising of the sun, that is, the dawn. So too, bhikkhus, for a bhikkhu this is the forerunner and precursor of the breakthrough to the Four Noble Truths as the really are, that is, right view. It is to be expected that a bhikkhu with right view will understand as it really is: ‘This is suffering.’… ‘This is the way leading to the cessation of suffering.’
“Therefore, bhikkhus, an exertion should be made to understand: ‘This is suffering.’… An exertion should be made to understand: ‘This is the way leading to the cessation of suffering.’”